Sophocles point in Oedipus

In Oedipus, Sophocles wanted to show that you shouldn't question the fate and the will of the gods.  He wanted to prove this, because what the gods have planned to do is bound to happen.  No one person is going to be able to change what the gods have planned for them, no matter how hard they try. 

In Oedipus, Oedipus tries changing his fate.  At first, he is in denial and he tries to blame Creon. In the play, Oedipus and Teiresias are arguing and Teiresias accuses Oedipus of being the murderer.  Oedipus was baffled that Teiresias had the guts to accuse him of being the murderer. As they keep arguing, Oedipus suspects Creon and asks Teiresias, "Was this your own design or Creon's?" This shows that Oedipus wants to get the blame off of himself.

Later on, Oedipus learns the truth about his life and what his fate was supposed to be. He learns that Jocasta, who is his wife, is really his real mother, who tried having him murdered when he was just a young baby but the messenger gave Oedipus to Merope and Polybus, who Oedipus grew up thinking were his real parents. So the story in Oedipus, is that no matter how hard you try to get rid of your fate, it is bound to happen. Oedipus' mother tried killing Oedipus so nothing would happen, but since the messenger didn't kill Oedipus the prophecy came true. Oedipus, unknowingly killed his father at the crossroads. He also married his mother, which was also supposed to happen.

So in the end, Sophocles' proved that fate is bound to happen. In Oedipus, fate was challenged and no matter what happened no one person could stop what was meant to happen. And even though Sophocles allowed characters in his stories to question the fate of the gods, he didn't allow the gods to be proven wrong (in Oedipus, at least) which was a good thing at that time, because no one had questioned the fate of the gods before.